Potassium Ferrate Research Articles

New insight into waste activated sludge acetogenesis triggered by coupling sulfite/ferrate oxidation with sulfate reduction-mediated syntrophic consortia

Acetate (HAc) production via acetogenesis is a promising biorefinery approach for waste activated sludge (WAS); however, it is hampered by the thermodynamic constraints of the bioconversion of 3–5 carbon atom short-chain fatty acids (SCFAs). Sulfate radical (SO4∙‾)-based advanced oxidation is regarded as an appropriate candidate for accelerating WAS fermentation. In this study, we enriched an incomplete-oxidative sulfate reducing bacteria (io-SRB), combined with SO4∙‾ oxidation (generated by potassium ferrate (PF) and sodium sulfite (Na2SO3)), to boost WAS acetogenesis. Generated sulfate during SO4∙‾ oxidation served as the necessary substrates for io-SRB metabolism. A proof-of-concept based on experimental data for the whole process is presented. Results confirmed that the PF + Na2SO3 + SRB test achieved the maximum SCFAs generation (4261 ± 210 mg COD/L with 60.9 ± 0.5% HAc) over the PF + Na2SO3 test without io-SRB mediation (2521 ± 109 mg COD/L with 50.6 ± 0.3% HAc). Particle size analysis and fluorescence spectroscopy indicated that PF + Na2SO3 oxidation had positive effects on accelerating soluble organics release. SO4∙‾ was the key radical, playing the most important role, as indicated by electron paramagnetic resonance and radical scavenging analysis. X-ray photoelectron spectroscopy revealed that io-SRB mediation further promoted the transformation of polysaccharides and proteins into carboxylic acids, based on SO4∙‾ oxidation. Moreover, 79% Fe(VI) was reduced to Fe(III), and most S(IV) was converted to SO42−, approximately 40% of which was metabolized by io-SRB consortium. Clearly, SO4∙‾ oxidation and io-SRB stimulation significantly altered the composition of the key microbiome, with fermentative acidogenic bacteria predominating. The possible synergistic relationships among io-SRB, hydrolyzing bacteria and acidogens were revealed by molecular ecological network analysis. This study provides new insights into the improvement of value-added bio-metabolite recovery from SO4∙−-based WAS fermentation.

Performance and Mechanism of Potassium Ferrate(VI) Enhancing Dark Fermentative Hydrogen Accumulation from Waste Activated Sludge

Potassium ferrate (K2FeO4, PF), as a multifunctional green oxidant, has been used for oxidative degradation of pollutants and recovery of resources in sludge. However, its impact on the generation of hydrogen in anaerobic fermentation of waste activated sludge (WAS) is still unclear. The purpose of this work is to study the influence of PF on the dark fermentative hydrogen production. Experimental result suggested that as PF increased from 0 to 0.09 g/g of TSS (total suspended solids), the maximal hydrogen production increased from 1.47 to 8.35 mL/g VSS (volatile suspended solids). A further increase to 0.12 g/g of TSS resulted in a decrease in hydrogen yield. Mechanism studies revealed that that the addition of PF not only facilitated the disruption of sludge cell and extracellular polymeric substances (EPS) but also increased the proportion of biodegradable organics, providing more bioavailable organics for subsequent reactions involved in hydrogen accumulation. Although the activities of microorganisms relevant to dark fermentation were suppressed to a certain extent in the presence of PF, the induced suppression to hydrogen consumers was more severe. Microbial studies indicated that the relative abundances of hydrogen producers (such as Petrimonas and Proteiniborus) were augmented while hydrogen consumers (such as Methanosaeta and Methylocaldum) decreased in the presence of PF.

Treatment of Bypass Wastewater Using Novel Integrated Potassium Ferrate(VI) and Iron Electrocoagulation System

AbstractBypass wastewaters in excess of plant capacity require in-plant wastewater treatment strategies capable of lessening the contamination magnitude prior to their discharge into water bodies. ...

One-step synthesis of biochar-supported potassium-iron catalyst for catalytic cracking of biomass pyrolysis tar

In this work, K–Fe bimetallic catalyst supported on porous biomass char was synthesized via a one-step synthesis method by pyrolysis of biomass (peanut shells) after impregnation of a small amount of potassium ferrate (PSC–K2FeO4), and was evaluated for the cracking of biomass pyrolysis tar. Control experiments using the pure char (PSC) and char-supported catalysts after impregnation of KOH (PSC–KOH) and FeCl3 (PSC–FeCl3) were also performed for comparison. The as-prepared PSC-K2FeO4 possessed a porous structure with the dispersion of particles/clusters of Fe metal, K2CO3 and KFeO2 on the char support. Tar cracking experiments showed that the PSC-K2FeO4 exhibited excellent catalytic activity on the cracking of biomass pyrolysis tar in the temperature range of 600–800 °C, and the obtained tar conversion efficiencies were obviously higher than that in the control experiments, particularly at relatively lower temperatures (600 and 700 °C). The yields of combustible gas compounds including CO, H2 and CH4 increased significantly using PSC-K2FeO4 as the catalyst due to the enhanced tar cracking and reforming reactions. The porous structure and the active crystal structures of the spent catalyst were well retained, indicating the potential for efficient and long-term utilization of the catalyst in tar cracking. PSC-K2FeO4 exhibited excellent reusability during the five times reuse under the same conditions without regeneration, which showed almost no obvious decrease in the tar conversion efficiency and gas yields.

Accelerating nutrient release and pathogen inactivation from human waste by different pretreatment methods

The limitation of hydrolysis and the health risks from pathogenic microorganisms are challenges in the treatment of human waste for volume reduction and nutrient recovery. In this study, potassium ferrate (PF), peroxymonosulfate (PMS), and PF combined with peroxymonosulfate (PMS+ PF) were used as pretreatment or co-treatment methods to enhance nutrient release and control pathogenic microorganisms in human waste. The PF pretreatment was the most effective regarding hydrolysis and organic matter release. The largest difference (D-value) in the soluble chemical oxygen demand (3117.0 mg/L) between the control and the treatment after 120 min was observed for the PF pretreatment, followed by the alkaline (ALK) pretreatment (1525.0 mg/L), the PF + PMS pretreatment (1169.3 mg/L), and the PMS pretreatment (1020.6 mg/L). The PF pre-treated waste exhibited the highest volatile solids reduction of 79.2% after 120 min compared with 15.0% reduction of the untreated waste, as well as the highest polysaccharide release, with a D-value of 198.5 mg/L. All pretreatments exhibited inactivation of pathogenic bacteria and helminths eggs; however, the PF pretreatment was the most efficient method to suppress pathogenic micrograms, with a 3.5 log (N/N0) decrease in the number of total coliforms. The PF pretreatment and PMS + PF co-treatment both exhibited the good performance regarding nitrogen release, including soluble protein and ammonium. The maximum D-value of the total soluble nitrogen was 372.8 mg/L for the PF + PMS co-treatment. The maximum D-value of soluble protein was 156.2 mg/L for the ALK pretreatment. The results indicated that the PF pretreatment was the most effective method for disintegrating human waste, thus providing a new method for safe and rapid reduction of human waste, as well as nutrient release.

Superior electrocatalytic performance of porous, graphitic, and oxygen-functionalized carbon nanofiber as bifunctional electrode for vanadium redox flow battery

Herein, a one-step method is applied to prepare porous, graphitic, and oxygen-functionalized carbon nanofiber as bifunctional electrode for vanadium redox flow battery (VRFB). Potassium ferrate is used to increase microporous structure, graphitization degree, and oxygen-containing group of carbon nanofiber synchronously at high temperature. This method is less time-demanding, highly efficient, and mild compared with typical two-step strategy (potassium hydroxide and ferric chloride treatment). Carbon nanofiber is modified at different mass ratio of carbon nanofiber and potassium ferrate (1:1, 1:3, and 1:5). The carbon nanofiber treated by one-step method with mass ratio of 1:3 (CNF-PF-3) demonstrates the best electrocatalysis towards V3+/V2+ redox reaction. Moreover, CNF-PF-3 also exhibits outstanding electrocatalysis towards VO2+/VO2+ redox reaction. The electrochemical performance of carbon nanofiber is improved by accelerating ion diffusion, electrochemical reaction, and electron transfer, systematically. It is due to an obvious increase in surface area, conductivity, active sites, and hydrophilcity for carbon nanofiber. The cell using CNF-PF-3 as bifunctional electrode presents the best energy storage performance compared with the cell using CNF-PF-3 at one side and pristine cell. Energy efficiency of the cell using CNF-PF-3 as bifunctional electrode reaches 75.5% at 100 mA cm−2, which is 9.9% higher than that of pristine cell.

Synthesis of Porous Biochar Containing Graphitic Carbon Derived From Lignin Content of Forestry Biomass and Its Application for the Removal of Diclofenac Sodium From Aqueous Solution.

Porous biochar containing graphitic carbon materials have received great attention from various disciplines, especially for environmental pollutant treatment, due to their cost-effective and specific textural properties. This study exhibited a two-step strategy to compose lignin-porous biochar containing graphitic carbon (LPGC) from pitch pine sawdust and investigated its adsorptive removal for diclofenac sodium (DCF) from an aqueous solution. Sulfuric acid (H2SO4) was utilized to obtain lignin content from biomass and potassium ferrate (K2FeO4) and was adopted to fulfill the synchronous carbonization and graphitization of LPGC. Through slow pyrolysis in atmospheric N2 (900°C – 2 h), the structure of the as-prepared sample was successfully modified. Using SEM images, a stripped layer structure was observed on the H2SO4-treated sample for both one-step and two-step activated samples, indicating the pronounced effect of H2SO4 in the layering of materials. K2FeO4 acted as an activator and catalyst to convert biomass into the porous graphitic structure. The BET surface area, XRD and Raman spectra analyses demonstrated that LPGC possessed a micro/mesoporous structure with a relatively large surface area (457.4 m2 g−1) as well as the presence of a graphitic structure. Further adsorption experiments revealed that LPGC exhibited a high DCF adsorption capacity (qmax = 159.7 mg g−1 at 298 K, pH = 6.5). The effects of ambient conditions such as contact time, solution pH, temperature, ionic strength, electrolyte background on the uptake of DCF were investigated by a batch adsorption experiment. Results indicated that the experimental data were best fitted with the pseudo second—order model and Langmuir isotherm model. Furthermore, the adsorption of DCF onto the LPGC process was spontaneous and endothermic. Electrostatic interaction, H-bonding interaction, and π-π interaction are the possible adsorption mechanisms. The porous biochar containing graphitic carbon obtained from the lignin content of pitch pine sawdust may be a potential material for eliminating organic pollutants from water bodies.

One-step prepared prussian blue/porous carbon composite derives highly efficient Fe–N–C catalyst for oxygen reduction

Preparation of high-efficiency oxygen reduction reaction (ORR) catalysts with abundant and inexpensive biomass materials have been a hot research topic. We use nitrogen-rich lentinus edodes and potassium ferrate (K2FeO4) to simultaneously activate the carbon material and prepare prussian blue (PB), and a porous carbon composite (PB/C) containing PB is synthesized. Finally, using ammonium chloride (NH4Cl) as a nitrogen source to further synthesize a Fe–N–C catalyst (PB/CN1T800) containing a trace amount of Fe for ORR. Results show that the prepared PB/CN1T800 catalyst forms a coral-like structure, which mainly contains mesopores and possesses a large specific surface area of approximately 1582 m2 g−1. Moreover, the onset potential of PB/CN1T800 is 0.95 V, and the half-wave potential is 0.83 V, which are consistent with those of commercial Pt/C. Thus the PB/CN1T800 material is an ORR catalyst with excellent performance. This work provides a basis for simple and efficient conversion of rich biomass into PB/porous carbon composites to prepare highly efficient catalysts.

Evaluation of enhanced coagulation combined with densadeg-ultrafiltration process in treating secondary effluent: Organic micro-pollutants removal, genotoxicity reduction, and membrane fouling alleviation

Conventional coagulation is widely used as an ultrafiltration membrane pretreatment process in wastewater reclamation, however it shows little ability to reduce organic micro-pollutants (OMPs) and genotoxicity. In this research, powdered activated carbon (PAC) and potassium ferrate were used respectively with polyaluminum chloride (PACl) to enhance coagulation. Filtration experiments of coagulation (CUF), coagulation-adsorption (CAUF) and coagulation-oxidation (COUF) pretreatment combined with densadeg-ultrafiltration processes were conducted under their optimum doses. The effluent water quality of CAUF and COUF could meet the water reuse quality standard for scenic environment use, while total phosphorus in the conventional CUF discharge was higher than the standard. The average removal efficiency of the selected fourteen OMPs was significantly improved by 1.8 times through the CAUF process compared to the CUF process (31.2%), whereas the COUF process (38.4%) showed limited improvement. Prominent reduction of genotoxicity was observed in the CAUF and COUF processes, and the effluent of the CAUF process had the least genotoxicity of 1.0 ± 0.3 μg 4-Nitroquinoline-N-oxide (4-NQO)/L. Moreover, the average transmembrane pressure increasing rate followed the order of CUF (1.5 kPa/d) > COUF (1.1 kPa/d) > CAUF (0.6 kPa/d), indicated that the enhanced coagulation process could relieve membrane fouling effectively.

Removal of aqueous As(III) Sb(III) by potassium ferrate (K2FeO4): The function of oxidation and flocculation

This study investigated the effects of potassium ferrate (K2FeO4) dosage, pH, and reaction time on the removal of aqueous As(III) and Sb(III), and revealed the oxidation and flocculation mechanism of K2FeO4. The results show that the removal efficiencies of As(III) and Sb(III) were highly related to the hydrolysate of K2FeO4 under acidic conditions, while the efficiencies were low under alkaline condition, owning to the electrostatic repulsion between iron nanoparticles and charged As/Sb species. The increased dosage and reaction time improved the adsorption performance. Based on the comparative experiments with FeCl3, the simultaneous removal of As(III) and Sb(III) by K2FeO4 suggested that As(III) was eliminated due to the processes of oxidation, flocculation, and chemical precipitation, while Sb(III) was removed mostly by oxidation and flocculation. The generated precipitates were characterized with surface analysis and the results support that the oxidization property of K2FeO4 was essential during the removal of As(III) and Sb(III), and removal mechanisms between both elements were different.

Co-treatment of potassium ferrate and peroxymonosulfate enhances the decomposition of the cotton straw and cow manure mixture

Since there is high lignocellulose content in the cotton straw and cow manure mixture (MCC), the appropriate MCC pretreatment is important to promote the anaerobic digestion (AD) hydrolysis. This study mainly explored the effect of potassium ferrate (PF) and peroxymonosulfate (PMS) pretreatments on MCC decomposition. PMS + PF co-treatment showed a higher reduction of total solid and volatile solid than PF pretreatment and PMS pretreatment. Hydrolysis of treated MCC indicated that the PF pretreatment was more effective to the release of organics than the PMS pretreatment and the PMS + PF co-treatment. However, the PMS + PF co-treatment resulted in a higher lignin removal rate (40.4%–50.5%) than the PMS pretreatment (30.8%) and the PF pretreatment (21.4%). The PMS1 + PF2 co-treatment (molar ratio of 1:2) acquired the optimal lignin removal rate and the release of organics among the PMS + PF co-treatment with different dosing ratio. Potential mechanism was that PF reduction products activated PMS to produce free radicals (SO4−, OH), which attacked lignocellulosic components and promoted MCC decomposition. The PMS1 + PF2 co-treatment was deduced to be the optimal pretreatment method when considering MCC decomposition, biodegradability, and mass transfer in the bioreactor.

Enhanced hydrogen production from food waste dark fermentation by potassium ferrate pretreatment.

Hydrogen generation from food waste anaerobic dark fermentation is identified as a promising strategy for resource recovery. In this work, an innovative strategy of using potassium ferrate (PF), a strong oxidant, to promote anaerobic dark fermentation of food waste to produce hydrogen has been reported. The experimental results revealed that PF enhanced the hydrogen production from food waste, the maximal hydrogen yield was 173.5mL/g, and the optimal PF dosage was 0.4g/g total suspended solids. PF shortened the lag phase for hydrogen generation from 120 to 96h. Mechanisms investigation revealed that PF accelerated the disintegration of organic compounds and increased the soluble organic matter in the liquid phase. The strong oxidation of PF inhibited the processes of hydrolysis, acidification, acetogenesis, homoacetogenesis, and methanogenesis by using synthetic wastewater in the fermentation process. The inhibition of PF on these processes was further verified by the enzyme activity analysis. Economic analysis indicated that 0.1g/g PF was the optimal dosage. PF treatment is a promising strategy to enhance the production of hydrogen from food waste dark fermentation.

Transformation and migration of phosphorus in excess sludge reduction pretreatment by alkaline ferrate oxidation combined with anaerobic digestion

Recently, more and more attention has been paid to the strong oxidation ability of newly prepared potassium ferrate (NAPF) in sludge reduction process, but less attention has been paid to the change of phosphorus in this process. The feasibility of phosphorus migration and transformation during excess sludge reduction pretreatment using NAPF pre-oxidation combined with anaerobic digestion was investigated. After 70 mg/g suspended solids NAPF pretreatment and 16 days anaerobic digestion, the solid-phase volatile suspended solids decreased by 44.2%, and much organic matter had been released into the liquid-phase and then degraded during digestion by indigenous microorganisms. As the sludge pre-oxidation process was performed, solid-phase organic phosphorus and chemically combined phosphorus also released into the liquid-phase as PO43−, peaking at 100 mg/L. During anaerobic digestion, the Fe3+ in the liquid-phase was gradually reduced to Fe2+, and then formed Fe2+-PO43− compound crystals and re-migrated to the solid-phase. The concentration of PO43− decreased to 17.08±1.1 mg/L in the liquid-phase after anaerobic digestion. Finally, the phosphorus in the Fe2+-PO43− compound accounts for 80% of the total phosphorus in the solid-phase. A large number of vivianite crystals in sludge were observed. Therefore, this technology not only effectively reduces sludge, but also increases the proportion of PO43− in the sludge in the form of Vivianite.

Biomass-derived porous carbons with tailored graphitization degree and pore size distribution for supercapacitors with ultra-high rate capability

It is extraordinarily valuable to develop the supercapacitor with high capacitance retention under ultra-high current density to meet the requirement of fast charging. Herein, porous carbons with tailored graphitization degree and pore size distribution are facilely prepared via controlling the activation temperature of biomass-derived pyrolytic carbon when employing potassium ferrate (K2FeO4) as catalyst and activation agent. The obtained semi-graphitized microporous carbon with a large specific surface area (2208 m2 g−1), high proportion of large micropores (more than 71.8%) and high conductivity (2.38 S cm−1) exhibits a perfect balance between the charge storage capacity and rate capability, which specific capacitance reaches 254 and 273 F g−1 at a current density of 0.5 A g−1 in KOH and H2SO4 aqueous electrolyte, respectively. Surprising capacitance retention of 86.9% is obtained under an ultra-large current density of 100 A g−1 for the symmetrical supercapacitor based on the semi-graphitized microporous carbon, and no apparent attenuation was observed after 10,000 cycles. Furthermore, energy density of the assembled symmetrical supercapacitor reaches 7.4 Wh kg−1 at a power density of 151.4 W kg−1, and more than 87.8% of energy density is kept even under an ultra-large power density of 29.1 kW kg−1.

Encapsulation of micro-sized barium ferrate(VI) and its effectiveness in removing clomazone pesticide from water

Synthesis of micro- and nano-sized crystalline BaFeO4 particles by precipitation from the electrochemically synthesized potassium ferrate(VI) solution by means of barium hydroxide and its encapsulation in paraffin wax were explored using scanning electron microscopy, X-ray diffraction spectroscopy and FTIR spectroscopy. Experimental results showed effective synthesis of the micro-sized and nano-sized BaFeO4 particles and their coating by the paraffin wax layer. The encapsulated micro- and nano-sized particles of BaFeO4 were applied in investigating the possibility of degradation of pesticide clomazone in water. The removal of clomazone from water by oxidation using encapsulated BaFeO4 could be almost 95%.

Application of porous biomass carbon materials in vanadium redox flow battery

Porous nano biomass carbon was synthesized by one-step method using scaphium scaphigerum as carbon source and was employed as negative catalyst for vanadium redox flow battery. Potassium ferrate was used to realize synchronous etching, introducing oxygen-containing groups and graphitization of scaphium scaphigerum to obtain porous, oxygen-rich, high-graphization carbon materials (SS-K/Fe). Compared with traditional two-step method, one-step method has advantages of low-time requirement, high efficiency and no pollution. The prepared SS-K/Fe sample has abundant microporous structure, high degree of graphitization and many oxygen-containing groups. The electrochemical test results show that the prepared carbon-based materials exhibit superior electrocatalytic capability for V2+/V3+ redox reaction. The electrode process can be accelerated from three steps including ion diffusion, electrochemical reaction and electron transfer processes, which are due to the enhancement of wetting performance and electrical conductivity, and an increase of effective catalytic area. Compared with pristine cell, the SS-K/Fe modified cell can improve the energy efficiency by 6.2% at the current density of 50 mA cm−2. This method is expected to realize low cost, green and renewable porous carbon materials for future energy storage systems.

New insight into enhanced production of short-chain fatty acids from waste activated sludge by cation exchange resin-induced hydrolysis

Recently, the production of short-chain fatty acids (SCFAs) from waste activated sludge (WAS) has received increasing attention. Although several pretreatment methods had been investigated, sludge hydrolysis through depletion of multivalent cations has rarely been reported. In this work, cation exchange resin (CER) was used for enhancing WAS hydrolysis and subsequent SCFAs production at various dosages of 0 to 3.5 g/g SS. With the addition of CER, the multivalent cations and trace metal elements (e.g. Ca2+, Mg2+, Fe3+, Zn2+, etc.) were removed from sludge through CER-mediated ion exchange, leading to disruption of extracellular polymeric substance (EPS), while triggering cell lysis which was evidenced by remarkable leakage of cellular DNA. This CER-mediated cyclic release-removal of multivalent cations resulted in substantial sludge hydrolysis with release of biodegradable organic matters. At the optimal CER dosage of 1.75 g/g SS, soluble COD (SCOD) was dramatically increased to 5944 mg/L (SCOD/TCOD = 34.7%) against 1440 mg/L in the control after 2-day fermentation. Meanwhile, a considerable SCFAs of 334.5 mg COD/g VSS was produced within the first 4 days of anaerobic fermentation, which was 3.3 times higher than that in the control. It was found that the acetic and propionic acids accounted for 57.4–65.4% of SCFAs produced in CER-assisted anaerobic fermentation. Compared to pretreatment with potassium ferrate, surfactant and enzymes, a much higher SCFAs concentration was obtained in this study with CER. In fact, used CER could be recovered and reused, without harsh chemicals left in fermented sludge. This indeed created an environmentally and economically beneficial situation with considerably saved pretreatment agents.

Synthesis a graphene-like magnetic biochar by potassium ferrate for 17β-estradiol removal: Effects of Al2O3 nanoparticles and microplastics.

A graphene-like magnetic biochar (GLMB) was synthesized using lotus seedpod and potassium ferrate with simple step and applied for E2 adsorption. GLMB was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and BET surface area. Several common (solution pH, ionic strength, humic acid and foreign ions) and new (Al2O3 nanoparticles and microplastics (MPs)) water experiment conditions were investigated. Characterization results demonstrated that the sample was fabricated successfully and it possessed some graphene-like properties and a large surface area (828.37m2/g). Adsorption results revealed that the pseudo-second-order kinetics and Langmuir isotherm models could provide a better description for E2 uptake behavior. The E2 adsorption capacity could be influenced by solution pH, ionic strength and SO42- ions, and the effect of humic acid and background electrolyte (Na+, K+, Ca2+, Mg2+, Cl-, NO3-, PO43-) could be neglected. The presences of Al2O3/MPs significantly decreased the time to reach adsorption equilibrium for E2 adsorption on GLMB, but had no obvious improvement or inhibiting effects on E2 removal when the adsorption reached equilibrium. The adsorption mechanism for E2 adsorption on GLMB was multiple, which involving π-π interactions, micropore filling effects, electrostatic interaction. The regeneration experiments showed that GLMB possessed a good regeneration performance. Based on the experimental results and comparative analysis with other adsorbents, GLMB was an economical, high-efficiency, green and recyclable adsorbent for E2 removal from aqueous solution.

Se(IV) oxidation by ferrate(VI) and subsequent in-situ removal of selenium species with the reduction products of ferrate(VI): performance and mechanism

In order to treat selenium pollution, the study presents the use of potassium ferrate (K2FeO4) as an environmentally friendly agent for in situ removal of Se(IV) from aqueous media. Batch experiments were carried out to evaluate the influences of various factors including dosage of K2FeO4, ex-situ and in-situ adsorption, initial pH, and adsorption isotherms. The results showed that increasing dosage of K2FeO4 benefited the removal of total selenium with the efficiency up to 97.0% and Se(IV) removal significantly depended on pH, and as the pH increases, the decrease in Se(IV) adsorption efficiency is a general trend of pH dependence. The X-ray powder diffraction, Fourier transformed infrared spectrometer and high-resolution X-ray photoelectron spectroscopy analysis indicated that Se(IV) was removed from the aqueous solution by adsorbing on the surface of the decomposition products of K2FeO4 which are ferric oxide nanoparticles, and the selenium adsorbed on the generated ferric oxide nanoparticles existed in the forms of Se(IV) and Se(VI). Se(IV) and Se(VI) were adsorbed to the decomposition products of K2FeO4 by forming an inner-sphere complexes and an outer-sphere complexes, respectively.

Controlling Disinfection By-Products Formation in Rainwater: Technologies and Trends

With an augmenting lack of pure water, rainwater has been viewed as an invaluable substitutional potable water fountain. The methods implemented for rainwater treatment are in control of the safety of potable water. Researchers examined various disinfection methods to estimate the monitoring of disinfection by-products (DBPs) generation. The tried disinfection techniques involved chlorination and chloramination, pre-oxidation by potassium permanganate (KMnO4) and potassium ferrate (K2FeO4), ultraviolet/hydrogen peroxide (UV/H2O2), and ultraviolet/persulfate (UV/PS) methods. In spite of low contaminants existing in rainwater comparatively with surface water, the same findings are mostly obtained in terms of DBPs production and control procedures using the above-mentioned technologies. Employing granular activated carbon post-treatment could greatly reduce the concentrations and poisonous effects of DBPs. Moreover, secure multi-barrier techniques, like distillation and membrane processes, remain to be suggested, tested and industrially encouraged.